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PLC control system grounding - Solutions - Huaqiang Electronic Network
The grounding system in a PLC control system plays a critical role in ensuring stable and reliable operation. It typically includes several types of grounds such as system ground, shield ground, AC ground, and protective ground. However, improper grounding can introduce significant interference into the system. One of the main issues arises from uneven potential distribution across different grounding points, which leads to a ground potential difference. This difference can cause ground loop currents, disrupting the normal functioning of the PLC.
For example, when dealing with RF cables, it's important to note that they can be customized to meet various specifications. In the case of cable shielding, proper grounding is essential. If both ends of the shielding layer are grounded, a ground potential difference between the two points can result in current flowing through the shielding. This issue becomes even more severe during abnormal conditions like lightning strikes, where the ground current can significantly increase.
Moreover, the shielding layer, grounding wire, and earth can form a closed loop. When exposed to changing magnetic fields, this loop may induce currents in the shielding layer. These currents can interfere with the signal integrity by coupling with the core wires. If the system shares a ground with other equipment, the resulting ground loops can create uneven potential distributions on the ground plane. This can affect both the logic and analog circuits within the PLC.
Since PLCs have low tolerance for voltage interference, even small fluctuations in the logic ground potential can disrupt their operations. This can lead to data corruption, program malfunctions, or even system crashes. To prevent such issues, it's crucial to implement a well-designed grounding strategy, ensuring that all grounds are properly connected and isolated where necessary. Proper shielding and grounding practices are key to maintaining the reliability and performance of PLC systems in industrial environments.